Mechanical and vacuum seed meters are commonly used in agricultural planters in the planting of crops. A typical mechanical seed meter includes a housing and a rotating assembly within the housing having plural spaced “fingers” about its outer periphery. Each finger is adapted to receive an individual seed and hold that seed in place through mechanical spring force. Each seed is then sequentially released from its finger through an opening in a wall of the housing for the seed to exit into the seed tube where it falls, under gravity, to a furrow formed in the ground. In other mechanical meters, when seed exits the housing it is received by a belt which carries and drops the seed down the seed tube where it falls, under gravity, to the furrow. Still further, certain other types of mechanical seed meters use a rotatable drum or fluted roll instead of fingers to meter seeds. These meters also sequentially release the seed through an opening in the housing, allowing the seed to drop to the ground under the influence of gravity.
A typical vacuum seed meter includes a rotating seed disc having plural spaced apertures about its outer periphery. Each aperture is adapted to receive an individual seed which is maintained in position in the aperture on a first side of the seed disc by means of a vacuum applied to a second, opposed sided of the disc. Each seed is sequentially released from its aperture in the seed disc by interrupting the applied vacuum, allowing the seed to drop to the soil under the influence of gravity.
Vacuum seed meters have, to varying degrees, various operating limitations because of their design and the environment in which they operate. For example, a high vacuum must be maintained across the seed disc to securely maintain the seeds in position on the seed disc until they are released. The applied vacuum must be interrupted completely and very abruptly to allow for the consistent and accurate release of the individual seeds to ensure proper seed positioning and inter-seed spacing. Irregularities in seed position and inter-seed spacing result in poor plant development and reduced crop production. Once the vacuum source is removed from holding the seed to the disc it is only under the influence of gravity and friction from the disc it was recently adhered to.
After a seed is dropped by the mechanical or vacuum seed meter, the seed then travels to the ground down the seed tube. Any contact between the seed and the tube walls can influence seed velocity and affect inter seed spacing. Furthermore, with respect to vacuum seed meters, influence of the seed disc interface and tangential velocity of the seed at release will influence the fore and aft position of the seed traveling down the seed tube. Wide ranges in meter rotational speeds due to varying crop types and planting speeds in conjunction with a fixed vacuum removal point only broaden the magnitude of the fore and aft variance of the seed in the seed tube aforementioned above.
Present seed sensors are located in the seed tube, which is disposed between the seed meter and the soil, and such seed sensors may only provide feedback when the seed crosses a predetermined plane on its travel to the ground. Sensing within the seed tube introduces certain factors that can skew desired data associated with the sensed seed. For example, when the seed contacts an interior surface of the seed tube, the path of the seed is altered and may skew the desired data to be sensed by the sensor. This skewed data may result in false readings relating to, for example, inter-seed spacing, falsely counting skips or doubles, etc. Moreover, the data provided by these present seed sensors may only serve in calculating seed to seed spacing.